Improvement in electric fuses



H. J. SMITH.

Electric Fuse. No. 112,859. i Patented March 21, 1871.-

4 r d I ILPETERS. PHGTO-LITNOGRAPNER. WASNINGYON- D. C.

ATENTFFICE.

HENRYJULIUS SMITH, OF BOSTON, MASSACHUSETTS.

IMPROVEMENT ELECTRIC FUSES.

Specification forming part of Letters Patent No. 112,859, dated March21, 1871; antedatcd March 7, 1871.

I, HENRY J ULIUs SMITH, of Boston, in the State of Massachusetts, haveinvented an Improvement in Electric Fuse, of which the following is aspecification:

' The invention consists in the peculiar construction of the fuse-head,whereby it is pro vided with two separate chambers or maga-i zines. I

It also consists in the employment of novel devices and means i forsecuring the wires within the fuse-head, whereby the fusehead itself ismade to serve as a shield to prevent communication between thoseportions of the fuse-wires which are just outside of the head.

On account of its high cost, it is desirable to use as little of thepriming employed in fuses as possible-that is, enough of it to make theignition of the fuse certain, but not enough of it to give as much flameas is desirable for igniting the blast. To increase the amount of flamethe fuse is charged with an inferior powder.

When fuses are to be used near the place of manufacture, the priming maybe placed in the same chamber with the inferior explosive material ofthe fuse; but when the fuses are transported any considerable distance,or are handled to any considerable extent, the lump of priming is apt tobe ground into dust, and by being diifused through the rest of thecharge its extraordinary capability of ignition is lost. By thisinvention the whole power of the priming is preserved.

In the drawing, Figure 1 is an exterior view of my fuse. Fig. 2 is asectional view taken at right angles to Fig. 1. Fig. 3 is a sectionalview of a modification of my invention.

The figures are enlarged to three times the actual size of the partsrepresented.

The shell of the fuse is of wood, and consists of two cups; but itdiffers from otherfuses made of two cups in having both cups in anupright position, the bottom of the smaller cup (marked B in thedrawing) fitting into the larger cup A, as shown in Fig. 2.

The smaller cup is bored out, so as to leave a thin bottom, as shown.Two nicks are then cut upon'opposite sides, about half-way from thebottom to the top of the cup, deep enough to make small holes at thebottom of each nick opening into the cup.

A minute lump of priming having been placed in the bottom of the cup,the extremities of the two wires 1) b of the fuse-cord are stripped oftheir insulating-covering, and after having their ends bent into hooks,as shown in Fig. 2, are pushed through the holes at the 7 bottom of thenicks.

A wooden plug, whose diameter is equal to that of the bore of the cup,is then driven into the cup far enough to leave a chamber, B, Fig. 2,only large enough to hold the priming, as shown.

The plug catches the two hooks and holds them in place near the bottomof the cup, at the same time keeping them far enough apart to break thecircuit for igniting the priming at the proper time. The plug fits thecup so closely that the wires are well secured within it. The smallercup, with the wires thus attached, is then driven into the larger cup,bottom downward, leaving a chamber, A, as shown in Fig. 2, containingthe powder or explosive compound, which has previously been placed inthe larger cup.

The operation of the fuse is as follows: The spark, passing from onewire to the other in the smaller chamber, passes through and ignites thepriming. The priming, exploding, blows out the bottom of the smallchamber, and ignites the powder in the large chamber. A second explosionfollows, which ignites the charge of the blast.

It will be observed that the small cup, with its wires and priming, asabove described, is in itself a fuse; and it is obvious that a fuseconsisting of one cup, with its wires entering through nicks and securedby a plug pushed in from the mouth, as above described, will be ofpractical use in blasting, when the chamber at the bottom is leftsufficiently large to hold the requisite charge.

The advantage gained by constructing a fuse with two separate chambersmay also be gained when the insulated wires of the cord pass in at themouth of the smaller cup, as shown in Fig. 3. In this case the ends ofthe wires are stripped of their coverings and bent into hooks, and arekept apart and secured to the fuse-head by along wooden plug, 0, asshown.

I am not aware that the fuse-wires have ever before been secured to thefuse-head by aplug driven into the mouth of the fuse, the plug at thesame time serving to insulate the wires and close up the magazine; butthe best way to unite thewires with thefuse-head is tomake use of theholes at the bottom of the nicks, cut as above described; and the nicksmay be cut with equal advantage, whether the smaller cup is driven intothe larger bottom downward, or whether it is inverted before beingdriving into the larger cup, or whether a cylinder is used in theplaceof the smaller cup, or whether the fuse-head consists of one cup.When the small cup is inverted, the stripped ends of the wires arepushed through the holes at the bottom of the nicks into the cup. A plugis then driven between the wires to the bottom of the cup, and the wiresare bent over the end of the plug, so as to come within a short distanceof each other. The advantage of having the fuse-head serve as a shieldbetween the wires outside of the fuse-head may be obtained by insertingthe wires through small holes made by boring directly through the sidesof the fuse-head into the chamber without cutting; but there is aliability to split the wood, which is avoided by the use of the nick.

I am aware that I am not the first to make a fuse consisting of twochambers, and I wish to limit my invention in this respect to my twoshells, one being a fuse in itself, as herein described, and fittingclosely within the other, as specified. v

I claim 1. Afuse constructed with two chambers,

when the shell forming one of the chambers,

with its wires and charge, forms an independent fuse, as described, andfits closely within the shell containing the common powder, asspecified.

2. Attaching the wires by passing them through the sides of thefuse-head,substantially as described.

3. A nick or nicks cut into the side of the fuse, substantially asdescribed, for the purpose described.

4. Securing the fuse-wires to the fuse-head by a plug driven into themouth of the fuse, when the plug insulates the wires and closes themagazine, substantially as shown in Fig. 3.

5. Afuse consisting of one cup,with its wires, entering through thesides, and secured by a plug pushed in from the mouth, substantially asdescribed,

H. JULIUS SMITH.

